1. Field of the Invention
This invention relates to compositions useful for making filtration membranes, for example those used to separate materials in fluids.
2. Background
Freshwater scarcity, widespread pollution, and stricter governmental regulations have created an increased need for the development of advanced water treatment technologies including fluid separation processes. Fluid separation processes are also widely used in a variety of academic and industrial environments. Consequently, compositions, devices and associated techniques that facilitate the efficient separation of components in fluid mixtures have an expanding variety of applications. For these reasons, improved materials and techniques for the separation of components of fluid mixtures are highly desirable.
Filtration is a common separation technology that is typically used to remove constituents such as particulates (e.g. organisms, colloidal matter and the like) from fluids. Two basic filter types exist: media (depth) filters and membrane (sieving) filters. Media filters are a well established technology for use in water purification which typically rely on cheap, natural media such as sand, anthracite, crushed magnetite, garnet, etc. to treat wastewater (see, e.g. Droste, Theory and practice of water and wastewater treatment. 1997, John Wiley & Sons, Inc.: New York, N.Y. p. 416-451). While membrane filtration also has been used to purify drinking water for over 50 years, the vast majority of modern water and wastewater treatment plants continue to use granular media filters.
Granular media filters have limitations in a number of contexts. For example, particle removal in depth filters is limited by the effectiveness of coagulation. Moreover, as the media in such systems is not fixed within the filter bed, the presence of some contaminating constituents in such systems can occur. Contaminations of drinking water such as the Cryptosporidium protozoan outbreak in Milwaukee in 1993 have resulted in epidemics of waterborne disease that highlighted this Achilles heel of media filtration, i.e. their intrinsically poor removal of particles in the micrometer size range especially when coagulation is sub-optimal (see, e.g., Corso et al., 2003, 9, 426-431). Such contamination events have forced public health officials and the water industry to consider replacing granular media filters with membrane filtration, which (relative to media filtration) can offer an enhanced barrier to a wide variety of contaminants. In addition, in other types of separation processes, membranes offer a greater ability to selectivity tailor filtration characteristics by, for example, modifying the surface pore structure and surface chemistry.
In view of the wide variety of technologies in which the use of membranes for the separation of components in a fluid medium is desirable, there is a need in the art for membrane materials having enhanced properties that optimize their use in such contexts.